Allergen vaccine proteins for the treatment and prevention of allergic diseases

ABSTRACT

The present invention provides fusion proteins comprising an allergen sequence linked via an IgG hinge region to another polypeptide sequence capable of specifically binding to a native IgG inhibitory receptor containing an immune receptor tyrosine based inhibitory motif (ITIM). They are designed to cross-link an Fc receptor for IgE (e.g., FcεR1) and an IgG inhibitory receptor (e.g., FcγRIIb), thereby inhibiting the IgE-driven mediators released from mast cells and basophils. In addition, the present invention provides nucleic acid molecules encoding the fusion proteins, vectors and host cells for producing the fusion proteins, pharmaceutical compositions comprising the fusion proteins, and methods for ameliorating or reducing the risk of IgE-medicated allergic diseases.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 USC 119(e) of U.S. Provisional Patent Application No. 60/694,022, filed Jun. 23, 2005, where this provisional application is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to allergen vaccines, and more particularly to allergen vaccines that utilize fusion proteins in the treatment and prevention of allergic diseases.

2. Description of the Related Art

An allergy is an immune system reaction to a typically harmless substance. The immune system is always working to fight off parasites, fungi, viruses and bacteria. However, sometimes the immune system will treat a harmless substance (called an allergen) as an unwanted invader and try to fight it. This overreaction of the body's immune system to a typically harmless substance is called an allergic reaction.

Different allergies have different names, according to where they occur in the body. There are five common types of allergies, namely, allergic rhinitis, allergic dermatitis, asthma, food allergies and urticaria.

Allergic rhinitis affects the eyes, nose and sinuses. It causes stuffy or runny nose, ears and throat postnasal, watery or itchy eyes, and bronchial tube irritation, also known as hay fever. Allergic dermatitis affects the skin, causing an itchy rash. It is also known as contact dermatitis. Asthma affects the lungs, causing shortness of breath or wheezing. Food allergies affect the stomach and other internal organs, and may also cause symptoms to the entire body. Urticaria is a condition resulting with hives on the skin.

Almost anything can act as an allergen. However, some substances are very common allergens, such as, pollen and mold, dust mite droppings, pet allergens, food allergies, insect stings, and cockroach sensitivities. About a quarter of all Americans are genetically predisposed to allergic reactions from airborne pollen and mold. Dust mites, which are tiny spider-like creatures, leave droppings on bedsheets, pillows, and furniture. It is found that at least twenty million Americans are allergic to dust mite droppings, making it the next most common allergen. Around fifteen to thirty percent of people with allergies are found to be allergic to the third most popular allergens, pet allergens. They are sensitive to the proteins in pet dander (dead skin), pet saliva and pet urine. Those with dog allergies may be allergic to all dogs, or just certain breeds, but those with cat allergies are generally allergic to all cats. Cat allergies are about twice as common as dog allergies, affecting about six to ten million Americans.

Sensitivities to certain foods affect three to eight percent of children and one to two percent of adults. Ninety percent of all food allergies are caused by eight types of food, namely, milk, soy, eggs, wheat, peanuts, tree nuts, fish and shellfish. A few food preservatives also cause allergic reactions, namely, monosodium glutamate (found in many Asian foods, bouillon cubes and other preserved meat products) and metabisulfites (found in wines, particularly red wines). Insect stings from bees, wasps, fire ants, and the like, can be life threatening, and about two million Americans are prone to these allergic reactions. The toxins from the sting can cause severe reactions ranging from hives, wheezing, itching, swelling of the tongue, or even cardiac arrest. Cockroach sensitivies result when a cockroach crawls over food, or when cockroach droppings become airborne, and such allergens are ingested or inhaled, causing an allergic reaction. Anywhere from twenty-three to sixty percent of urban asthma sufferers are allergic to cockroach allergens.

It is important to realize that allergies are not only troublesome during the pollen season, but can be debilitating and become chronic disorders, which can have a negative long-term effect on one's health, pocketbook and happiness. Allergies should be taken seriously, and it is important to learn more about it.

Many allergies are passed onto children genetically through their parents. There is a one in three chance of developing some sort of allergy if the parent has the allergy (although not necessarily to the same allergen), according to the Asthma and Allergy Foundation of America. And if both parents have allergies, the child has a seventy percent chance of developing allergies. The substances that a person is allergic to depend on one's own genetic makeup, as well as one's exposure. Another factor is age. It was found that the peak age for developing an allergy seems to be around age nineteen.

One type of allergic reaction that requires special attention is anaphylaxis, which is sudden, severe, and potentially fatal, with symptoms that can affect various areas of the body. The symptoms usually appear very quickly after exposure to the allergen and can include intense itching all over the body, full-body swelling, respiratory distress, and can even lead to life threatening shock.

These reactions demand prompt medical attention and may require not only antihistamines and corticosteroids for relief, but also a form of adrenaline known as epinephrine. People who are highly susceptible to anaphylactic reactions should always carry a syringe of epinephrine with them and wear a medical alert bracelet.

A hallmark of the allergic diathesis is the tendency to maintain a persistent IgE response after antigen (allergen) presentation. The initial exposure to antigens stimulates the production of specific IgE molecules, which bind to high-affinity Fc receptors on the surface of mast cells. Upon reexposure of antigens, the cross-linking of antigens and membrane-bound IgE molecules result in the release of vasoactive mediators, setting off subsequent clinical manifestation of sneezing, pruritus, and bronchospasm. Immunoglobulin receptors (also referred to as Fc receptors), are cell-surface receptors of mast cells, that bind to the constant region of immunoglobulins, and mediate various immunoglobulin functions other than antigen binding.

Fc receptors that bind with IgE molecules (a type of immunoglobulin) are found on many types of cells in the immune system. There are two different Fc receptors currently known for IgE, the multichain high-affinity receptor, FcεRI, and the low-affinity receptor, FcεRII. IgE molecules mediate its biological responses as an antibody through these Fc receptors. The high-affinity FcεRI receptor, expressed on the surface of mast cells, basophils, and Langerhans cells, belongs to the immunoglobulin gene superfamily, and has a tetrametric structure composed of an α-chain, a β-chain and two disulfide-linked γ-chains that are required for receptor expression and signal transduction. The α-chains of the receptor interact with the distal portion of the third constant domain of the IgE heavy chain. The specific region of the human IgE molecule involved in binding to the human FcεRI receptor have been identified as including six amino acids, Arg-408, Ser-411, Lys-415, Glu-452, Arg-465, and Met-469. The interaction is highly specific with a binding constant of about 10¹⁰M⁻¹.

The low-affinity FcεRII receptor, represented on the surface of inflammatory cells, such as eosinophils, leukocytes, B lymphocytes, and platelets, did not evolve from the immunoglobulin superfamily but has substantial homology with several groups of animals and is made up of a transmembrane chain with an intracytoplasmic NH₂ terminus. The low-affinity receptor, FcεRII (CD23), is currently known to have two forms, FcεRIIa and FcεRIIb, both of which have been cloned and sequenced. The two forms differ only in the N-terminal cytoplasmic region, with the extracellular domains being identical. FcεRIIa is normally expressed on B cells, while FcεRIIb is expressed on T cells, B cells, monocytes and eosinophils upon induction by the cytokine IL-4.

Through the high-affinity FcεRI receptor, IgE plays key roles in an array of acute and chronic allergic reactions, including asthma, allergic rhinitis, atopic dermatitis, severe food allergies, chronic urticaria and angioedema, as well as the serious physiological condition of anaphylactic shock. The binding of a multivalent antigen to an antigen-specific IgE molecule, which is specifically bound to a FcεRI receptor on the surface of a mast cell or basophil, stimulates a complex series of signaling events that culminate in the release of host vasoactive and proinflammatory mediators that contributes to both acute and late-phase allergic responses.

The function of the low-affinity FcεRII receptor (also referred to as CD23), found on the surface of B lymphocytes, is less well-established than that of the FcεRI receptor. FcεRII, in a polymeric state, binds to IgE molecules, and this binding may play a role in controlling the type (class) of antibody produced by B cells.

Three groups of Fcγ receptors that bind to the constant region of human IgG molecules have so far been identified on cell surfaces. They are, FcγRI (CD64), FcγRII (CD32), and FcγRIII (CD16), all of which belong to the immunoglobulin gene superfamily. The three Fcγ receptors have a large number of various isoforms.

In addition to the stimulatory FcεRI receptor, mast cells and basophils also co-express an immunoreceptor tyrosine-based inhibition motif (ITIM)-containing inhibitory low-affinity receptor, called the FcγRIIb receptor, which act to negatively regulate antibody functions. The FcγRIIb receptor belongs in the inhibitory receptor superfamily (IRS), which is a growing family of structurally and functionally similar inhibitory receptors that negatively regulate immunoreceptor tyrosine-based activation motif (ITAM)-containing immune receptors and a diverse array of other cellular responses. Coaggregation of an IRS member (such as FcγRIIb receptor) with an activating receptor (such as FcεRI receptor) leads to phosphorylation of the characteristic ITIM tyrosine and subsequent recruitment of the SH2 domain-containing protein tyrosine phosphatases SHP-1 and SHP-2, and the SH2 domain-containing phospholipases, SHIP and SHIP2. Possible outcomes of the coaggregation include inhibition of cellular activation, as demonstrated by the coaggregation of FcγRIIb and B-cell receptors, T-cell receptors, and activating receptors, such as FcεRI and cytokine.

A key contributor to asthma, allergic rhinitis and severe food reactions is the induced IgE-driven mediators released from mast cells and basophils. The cross-linking of a mast cell or basophil FcεRI receptor with a multivalent antigen, activates tyrosine phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) in the β- and γ-FcεRI subunit cytoplasmic tails, thereby initiating downstream signaling through Syk. Mast cells and basophils also express the FcγRIIb receptor, which contains a single conserved immunoreceptor tyrosine-based inhibition motif (ITIM) within its cytoplasmic tail. Studies indicate that the aggregating of FcγRIIb to FcεRI leads to rapid tyrosine phosphorylation of the FcγRIIb ITIM tyrosine by FcεRI-associated Lyn and inhibition of FcεRI signaling. This hypothesis has been supported in experiments using human Ig Fcγ-Fcε fusion proteins that directly cross-link the FcεRI and FcγRIIb receptors on human basophils.

Treatments of allergies include avoidance, immunotherapy, and allergy medications. The best course may simply be avoiding any allergens. Minimizing exposure can make a significant difference to allergy sufferers. However complete avoidance is not always possible.

Immunotherapy, also known as allergy shots, can help built allergy resistance. However immunotherapy is expensive and may take several years to take effect on the allergies. For most allergy sufferers, medications that treat allergy symptoms are a much better option.

Allergy medications can sometimes control the symptoms with over-the-counter or prescription medications. The treatment of allergy such as severe asthma is still a serious medical challenge. In addition, many of the therapeutics currently used in allergy treatment have serious side-effects. Common allergy medications include corticosteroids, steroid nasal sprays, antihistamines, decongestants, decongestants combined with antihistamines, cromolyn sodium and ipratropium bromide.

Doctors and allergy sufferers are anxiously awaiting the FDA to approve an Anti-IgE compound called omalizumab (brand name Xolair) for the treatment of allergic asthma. Omalizumab is the first anti-IgE drug submitted for FDA approval, although more are on the horizon.

Anti-IgE drugs are a breakthrough in allergy treatment for those with severe year-round allergies. Basically, the anti-body contained in anti-IgE drugs binds to the IgE circulating in the body after exposure to an allergen. This binding of the medication with the IgE prevents and the IgE from binding to mast cells and triggering mast cell rupture. The mast cells then remain intact, preventing the release of the histamine, prostaglandins and leukotrienes that cause allergy symptoms. In other words, instead of treating symptoms after they've already occurred. Anti-IgE drugs will prevent symptoms from occurring at all.

When approved, anti-IgE injections are expected to eventually replace traditional allergy immunotherapy injections. They offer a distinct advantage over traditional shots. Instead of doctors having to diagnose allergies precisely and administer specific solutions of those antibodies, anyone suffering from allergies can get a standard anti-IgE shot which will work to prevent allergic reactions, no matter what type. There are some side effects and very expensive.

Some prescription medications are avoidable to help control allergic rhinitis symptoms such as nasal steroids, antihistamines, and decongestants. But one of the newest forms of treatment for allergic rhinitis getting positive feedback are leukotrienses modifiers.

Leukotriene modifiers are not exactly new. But these drugs, originally approved to fight asthma, are proving effective in combating allergic rhinitis symptoms as well and are now being approved for that purpose.

Luekotriene modifier work by blocking the effects of leukotrienes, which are chemicals produced by certain cells in the body in response to an allergy. These leukotriene molecules contribute to the inflammation, swelling, airway constriction and production of mucus seen in allergic reactions. Leukotriene modifiers, which show a low incidence of side effects, are often prescribed in combination which steroids to prevent and treat allergy and asthma symptoms. In many cases, leukotriene modifiers help patients reduce their steroids dosage and help control symptoms such as itching, sneezing, wheezing and congestion.

Most US allergy sufferers who choose allergy immunotherapy treatment receive injections in their doctor's office. But an alternative therapy is getting good results in Europe. Instead of injections, allergy sufferers in France, Italy and Germany are prescribed allergen extract drops, which are concentrated dosages of the substance to which they are allergic, such as pollen. Allergy sufferers can place the drops under their tongue at home instead of visiting the doctor's office for shots.

The treatment is considered effective at controlling symptoms like wheezing, sneezing and runny noses that in Europe the French health care system use it for the treatment. Some American doctors are already using the drops system as well. But most American allergy sufferers will have to wait for FDA approval of the drops. The FDA is waiting for the results of ongoing studies of the drops before it initiates a formal review.

Although an anti-IgE antibody currently in clinical trials (rhuMAb-E26, Genentech, Inc.) and other experimental therapies such as antagonists of IL-4 show promising results, there is a need for the development of additional therapeutic strategies and agents to control allergic disease, such as asthma, severe food allergy, and chronic urticaria and angioedema.

One approach to the treatment of allergic diseases is by use of allergen-based immunotherapy. This methodology uses whole antigens as “allergy vaccine” and is now appreciated to induce a state of relative allergic tolerance. This technique for the treatment of allergy is frequently termed “desensitization” or “hyposensitization” therapy.

Increasing doses of allergic peptide are administered, typically by injection, to a subject over an extended period of time, frequently months or years. The mechanism of action of this therapy is thought to involve induction of IgG inhibitory antibodies, suppression of mast cell/basophil reactivity, the promotion of T-cell anergy, and/or clonal deletion, and in the long term, decrease in the levels of allergen specific IgE. The use of this approach is, however, hindered in many instances by poor efficacy and serious side effects including the risk of triggering a systemic and potentially fatal anaphylactic response, where the clinical administration of the allergen induces the severe allergic response it seeks to suppress. Thus, there exists a strong need to develop treatments for allergic diseases.

BRIEF SUMMARY OF THE INVENTION

The present invention provides fusion proteins that comprise an allergen sequence linked via an IgG hinge region to another polypeptide sequence capable of specifically binding to a native IgG inhibitory receptor containing an immune receptor tyrosine based inhibitory motif (ITIM). They are designed to cross-link an Fc receptor for IgE (e.g., FcεR1) and an IgG inhibitory receptor (e.g., FcγRIIb), thereby inhibiting the IgE-driven mediators released from mast cells and basophils (e.g., during the presentation of allergens). In addition, the present invention provides nucleic acid molecules encoding the fusion proteins, vectors and host cells for producing the fusion proteins, pharmaceutical compositions comprising the fusion proteins, and methods for ameliorating or reducing the risk of IgE-medicated allergic diseases.

In one aspect, the present invention provides a fusion protein comprising (i) a first polypeptide sequence capable of specifically binding to a native IgE molecule, (ii) a second polypeptide sequence capable of specifically binding to a native IgG inhibitory receptor comprising an immune receptor tyrosine based inhibitory motif (ITIM), and (iii) an IgG hinge region, wherein the first polypeptide sequence comprises an allergen sequence, and wherein the first polypeptide sequence and the second polypeptide sequence is functionally connected via the IgG hinge region.

In certain embodiments, the allergen sequence within the fusion protein is native cat allergen Fel d1 or a portion thereof. For example, the allergen sequence may comprise both a portion of native cat allergen Fel d1 chain 1 as set forth in SEQ ID NO:18 and a portion of native cat allergen Fel d1 chain 2 as set forth in SEQ ID NO:19.

In certain embodiments, the allergen sequence within the fusion protein is native mite allergen protein Der p1 as set forth in SEQ ID NO:4 or a portion thereof.

In certain embodiments, the allergen sequence within the fusion protein is native peanut allergen Ara has set forth in SEQ ID NO:10 or a portion thereof.

In certain embodiments, the IgG hinge region within the fusion protein is human IgG1 hinge region as set forth in SEQ ID NO:20.

In certain embodiments, the second polypeptide sequence is capable of specifically binding to a low-affinity IgG receptor FcγRIIb.

In certain embodiments, the second polypeptide within the fusion comprises the CH2 and CH3 portion of an IgG immunoglobulin heavy chain constant region. For example, the second polypeptide may comprise the CH2 and CH3 portion of human IgG1 immunoglobulin heavy chain constant region as set forth in SEQ ID NO:21.

In certain embodiments, the fusion protein is the protein referred to as “kitcin,” which has the amino acid sequence as set forth in SEQ ID NO:17.

In another aspect, the present invention provides nucleic acid molecules comprising nucleotide sequences encoding the fusion proteins described herein.

In certain embodiments, the nucleic acid molecule comprises a nucleotide sequence that encodes the kitcin fusion protein having the amino acid sequence as set forth in SEQ ID NO:17. For example, in certain embodiments, the nucleic acid molecule comprises the nucleotide sequence as set forth in SEQ ID NO:16.

In certain embodiments, the present invention provides vectors comprising and capable of expressing the nucleotide sequence encoding the fusion protein described herein.

In certain embodiments, the vector comprises and is capable of the nucleotide sequence encoding the katcin fusion protein as set forth in SEQ ID NO:17. For example, in certain embodiments, the vector comprises the nucleotide sequence as set forth in SEQ ID NO:16.

In another aspect, the present invention provides host cells transformed with the vectors described herein.

In another aspect, the present invention provides pharmaceutical compositions comprising a fusion protein described herein and a pharmaceutically acceptable ingredient.

In another aspect, the present invention provides methods for ameliorating or reducing the risk of an IgE-mediated allergic disease, comprising administering to a patient in need thereof an effective amount of a fusion protein described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary generic structure of an allergen vaccine protein.

FIG. 2 illustrates the structure of an exemplary mite allergen vaccine protein.

FIG. 3 illustrates the structure of an exemplary cat allergen vaccine protein.

FIG. 4 illustrates the structure of an exemplary peanut allergen vaccine protein.

FIG. 5 is a photograph that shows the results of a Western blot analysis of katcin fusion proteins purified from different clones that were probed with mouse anti-Fel d1 monoclonal antibody and goat anti-mouse antidody conjugated with horseradish peroxidase.

FIG. 6 is a graph that shows the results of an ELISA analysis of katcin fusion proteins purified from different clones. The purified proteins were loaded into a plate coated with mouse anti-Fel d1 antibody and detected with alkaline phosphatase-conjugated goat anti-human IgG Fc antibody.

FIG. 7 is a photograph that shows the results of a passive cutaneous anaphylaxis analysis of the katcin fusion protein in a monkey. The monkey was sensitized with cat allergic serum plus different doses of katcin or human IgE. After 4 hours, the monkey was intravenously challenged with purified Fel d1 plus Evans blue. Cutaneous anaphylaxis was assessed visually by the blue dye leakage from blood vessels into the skin.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides fusion proteins capable of cross-linking an Fc receptor for an IgE (e.g., FcεR1) and an IgG inhibitory receptor that contains an IMIT (e.g., FcγRIIb), thereby inhibiting the IgE-driven mediators released from mast cells and basophils. In addition, the present invention provides nucleic acid molecules encoding the fusion proteins, vectors and host cells for producing the fusion proteins, pharmaceutical compositions comprising the fusion proteins, and methods for ameliorating or reducing the risk of IgE-mediated allergic diseases or other disorders.

In one aspect, the present invention provides a fusion protein comprising (i) a first polypeptide sequence capable of specifically binding to a native IgE molecule, (ii) a second polypeptide sequence capable of specifically binding to a native IgG inhibitory receptor comprising an immune receptor tyrosine based inhibitory motif (ITIM), and (iii) an IgG hinge region, wherein the first polypeptide sequence comprises an allergen sequence, and wherein the first polypeptide sequence and the second polypeptide sequence is functionally connected via the IgG hinge region. Because by specifically binding to the native IgE molecule, the first polypeptide is indirectly bound to an IgE receptor for the native IgE molecule (e.g., FcεRI receptor) via the native IgE molecule, the fusion protein is capable of cross-linking the IgE receptor with the IgG inhibitory receptor.

The term “immunoglobulin (Ig)” refers to the immunity-conferring portion of the globulin proteins of serum, and to other glycoproteins that have the same functional characteristics.

The term “IgG” refers to one of Ig isotypes found in serum, which is the main antibody raised in response to an antigen and has four major subtypes, IgG₁, IgG₂, IgG₃ and IgG₄.

The term “IgE” refers to one of Ig isotypes found in serum, which binds tightly to mass cell and basophils, and when additionally bound to antigen, causes release of histamine and other mediators of immediate hypersensitivity. This isotype of Ig plays a primary role in allergic reactions such as hay fever, asthma and anaphlaxis.

Immunoglobulin sequences, including their heavy chain constant regions, are well known in the art (see, Kabat et al., Sequences of Proteins of Immunological Interest, 5^(th) Ed. Public Health Service, National Institute of Health, Bethesda, Md., 1991). Additional references include Ellison et al., Nucl. Acid Res. 10:4071-4079, 1982 (for the human IgG₁ heavy chain constant region); Takahashi et al., Cell 29:671-679, 1982 (for the human IgG₁, IgG₂, IgG₃, and IgG₄ heavy chain constant regions); Krawinkel et al., EMBO J. 1:403-407, 1982 (for the human IgG₂, IgG₃, IgG₄ heavy chain constant regions); Ellison et al., Proc. Nat. Acad. Sci. USA 79:1984-1988, 1982 (for the human IgG₂ heavy chain constant region); Ellison et al., DNA 1:11-18, 1982 (for the human IgG₄ heavy chain constant region); Max et al., Cell 29:691-699, 1982 (for the human IgE heavy chain constant region); Saxon et al., J. Immunol. 147:4000, 1991 (for IgE isoforms); Peng et al., J. Immunol. 148:129-136, 1992 (for IgE isoforms); Zhang et al., J. Exp. Med. 176:233-243, 1992 (for IgE isoforms); and Hellman, Eur. J. Immunol. 23:159-167, 1992 (for IgE isoforms).

The term “inhibitory receptor” refers to a receptor capable of down regulating a biological response mediated by another receptor.

The term “immune receptor tyrosine based inhibitory motif (ITIM)” refers to a motif generally represented by the formula Val/lle-Xaa-pTyr-Xaa-Xaa-Leu/Val, where Xaa represents any amino acid.

The term “IgG inhibitory receptor” refers to a member of the inhibitory receptor superfamily capable of attenuating an FcεR-mediated response.

The term “IgG inhibitory receptor comprising an ITIM” refers to an IgG inhibitory receptor that contains an ITIM. Exemplary IgG inhibitory receptors include low-affinity FcεRIIb receptor and gp49b1.

A “native” protein (e.g., an immunoglobulin protein or its receptor) refers to a naturally occurring protein.

A polypeptide specifically binds to another polypeptide (e.g., a native IgE molecule or a native IgG inhibitory receptor) if it binds to the other polypeptide with a binding constant of at least 10⁶M⁻¹ (e.g., 10⁷M⁻¹, 10⁸M⁻¹, 10⁹M⁻¹, and 10¹⁰M⁻¹).

The term “allergen” refers to specific antigens capable of inducing IgE-mediated allergies. Exemplary allergens include those found in food, pollen, house dust, and dander from house pets.

As indicated above, the first polypeptide sequence of the fusion protein comprises an allergen sequence. The allergen sequence may be a naturally occurring allergen sequence, a portion of a naturally occurring allergen sequence, or a variant of a naturally occurring allergen sequence, that is capable of specifically binding to an allergen-specific IgE molecule.

In certain embodiments, the first polypeptide sequence comprises an allergen sequence with an at least 80%, 85%, 90%, 95%, or 99% sequence identify with a naturally occurring allergen sequence or a portion thereof that is capable of binding to an allergen-specific IgE molecule.

“Sequence identity” is defined as the percentage of amino acid residues in one sequence that are identical with the amino acid residues in another reference polypeptide sequence after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. The percentage sequence identity values are generated by the NCBI BLAST2.0 software as defined by Altschul et al., (1997), “Gapped BLAST and PSI-BLAST: a new generation of protein database search programs”, Nucleic Acids Res., 25:3389-3402 with the parameters set to default values.

The sequences of a large number of allergens are known in the art. Exemplary allergens include mite allergen Der p1 (see, SEQ ID NOS:3 and 4 for its nucleotide and amino acid sequences), cat allergen Fel d1 (see, SEQ ID NOS:5 and 6 for the nucleotide and amino acid sequences of its chain 1, and SEQ ID NOS:7 and 8 for the nucleotide and amino acid sequences of its chain 2), and peanut allergen Ara h (see, SEQ ID NOS:9 and 10 for its nucleotide and amino acid sequences). Numerous other allergens and their sequences are available from the SWISS-PROT database, some of which are listed in Table 1 of U.S. Patent Application Publication No. US 2003/0082190 (which is incorporated herein by reference).

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises native cat allergen Fel d1 or a portion thereof. For example, in certain embodiments, the first polypeptide sequence comprises both a portion of native cat allergen Fel d1 chain 1 as set forth in SEQ ID NO:18 and a portion of native cat allergen Fed d1 chain 2 as set forth in SEQ ID NO:19.

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises a sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with native cat allergen Fel d1 or a portion thereof and capable of specifically binding to a cat allergen Fel d1-specific IgE antibody.

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises both a sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with native cat allergen Fel d1 chain 1 and another sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with native cat allergen Fel d1 chain 2, wherein the first polypeptide is capable of specifically binding to a cat allergen Fel d1-specific IgE antibody.

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises native mite allergen protein Der p1 as set forth in SEQ ID NO:4 or a portion thereof.

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises a sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with native mite allergen protein Der p1 set forth in SEQ ID NO:4 or a portion thereof and capable of specifically binding to a mite allergen protein Der p1-specific IgE antibody.

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises native peanut allergen Ara h as set forth in SEQ ID NO:10 or a portion thereof.

In certain embodiments, the first polypeptide sequence of the fusion protein of the present invention comprises a sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with native peanut allergen Ara h as set forth in SEQ ID NO:10 or a portion thereof and capable of specifically binding to a peanut allergen Ara h-specific IgE antibody.

The second polypeptide sequence in the fusion protein of the present invention is capable of specifically binding to a native IgG inhibitory receptor comprising an ITIM, such as FcγRIIb receptor and gp49b1.

In certain embodiments, the second polypeptide sequence comprises the CH2 and CH3 portion of human IgG immunoglobulin heavy chain constant region. In certain embodiments, the second polypeptide sequence comprises the CH2 and CH3 portion of human IgG₁ immunoglobulin heavy chain constant region as set forth in SEQ ID NO:21. In certain other embodiments, the second polypeptide sequence comprises the CH2 and CH3 portion of human IgG₂, IgG₃, or IgG₄ immunoglobulin heavy chain constant region.

In certain embodiments, the second polypeptide sequence comprises a sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with the CH2 and and CH3 portion of human IgG immunoglobulin heavy chain constant region. In certain embodiments, the second polypeptide sequence comprises having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with the CH2 and CH3 portion of human IgG₁ immunoglobulin heavy chain constant region as set forth in SEQ ID NO:21 and capable of specifically binding to a native IgG inhibitory receptor containing an ITIM (e.g., FcεRIIb). In certain other embodiments, the second polypeptide sequence comprises a sequence having an at least 80%, 85%, 90%, 95%, or 99% sequence identity with the CH2 and CH3 portion of human IgG₂, IgG₃, or IgG₄ immunoglobulin heavy chain constant region and capable of specifically binding to a native IgG inhibitory receptor containing an ITIM (e.g., FcεRIIb).

The first and second polypeptides of the fusion protein of the present invention are functionally connected via an IgG hinge region.

The term “IgG hinge region” refers to the hinge region of a native IgG immunoglobulin heavy chain constant region, a portion of the hinge region of a native IgG immunoglobulin heavy chain constant region that consists of at least 10 consecutive amino acid residues (e.g., 10, 11, 12, 13, or 14 amino acid residues), or a sequence that has an at least 80% (e.g., 80%, 85%, 90%, 95%, or 99%) sequence identity with the hinge region of a native IgG immunoglobulin heavy chain constant region or a portion thereof that consists of at least 10 consecutive amino acid residues (e.g., 10, 11, 12, 13, or 14 amino acid residues).

The first polypeptide of the fusion protein of the present invention is “functionally connected” to the second polypeptide if in the resulting fusion protein, the first polypeptide is still capable of specifically binding to a native IgE molecule, and the second polypeptide is still capable of specifically binding to a native IgG inhibitory receptor comprising an ITIM.

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention are functionally connected via the hinge region of an IgG₁ immunoglobulin. For example, the first and second polypeptides may be functionally connected via the 15 amino acid hinge region of human IgG₁ immunoglobulin as set forth in SEQ ID NO:20.

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention are functionally connected via a portion of the hinge region of an IgG₁ immunoglobulin (e.g., human IgG₁ immunoglobulin) that consist of at least 10, 11, 12, 13, or 14 amino acid residues.

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention are functionally connected via a sequence having an at least 80%, 85%, 90%, 95%, 99% of the hinge region of an IgG₁ immunoglobulin (e.g., human IgG₁ immunoglobulin) or a portion thereof that consists of at least 10 consecutive amino acid residues (e.g., 10, 11, 12, 13, or 14 amino acid residues).

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention are functionally connected via the hinge region of an IgG₂, IgG₃, or IgG₄ immunoglobulin. For example, the first and second polypeptides may be functionally connected via the hinge region of human IgG₂, IgG₃, or IgG₄ immunoglobulin as set forth in SEQ ID NO:22, 23, or 24.

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention are functionally connected via a portion of the hinge region of an IgG₂, IgG₃, or IgG₄ immunoglobulin (e.g., human IgG₂, IgG₃, or IgG₄ immunoglobulin) that consist of at least 10, 11, 12, 13, or 14 amino acid residues.

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention are functionally connected via a sequence having an at least 80%, 85%, 90%, 95%, 99% of the hinge region of an IgG₂, IgG₃, or IgG₄ immunoglobulin (e.g., human IgG₂, IgG₃, or IgG₄ immunoglobulin) or a portion thereof that consists of at least 10 consecutive amino acid residues (e.g., 10, 11, 12, 13, or 14 amino acid residues).

In certain embodiments, the first and second polypeptides of the fusion protein of the present invention may be linked with an IgG hinge region so that the first polypeptide is located N-terminus to the second polypeptide. In certain other embodiments, the first polypeptide may be linked to the second polypeptide via an IgG hinge region so that it is C-terminus to the second polypeptide.

In certain embodiments, the fusion proteins of the present invention is capable of (1) indirect binding of a native high-affinity FcεR1 receptor via directly binding between a native IgE molecule to which the native high-affinity FcεR1 receptor binds and the first polypeptide sequence in the fusion protein, and (2) direct binding of a native low-affinity FcγRIIb receptor via the second polypeptide sequence in the fusion protein.

In certain embodiments, the fusion protein of the present invention comprises an allergen sequence and the CH2 and CH3 portion of human IgG₁ heavy chain constant region linked by the hinge region of human IgG₁ heavy chain constant region (see, FIG. 1). The cDNA sequence encoding the hinge-CH2—CH3 portion of the human IgG₁ heavy chain constant region and the amino acid sequence of this portion of the human IgG₁ heavy chain constant region are set forth in SEQ ID NOS:1 and 2, respectively.

In certain embodiments, the fusion protein of the present invention comprises mite allergen protein (or a portion thereof) and the CH2 and CH3 portion of human IgG₁ heavy chain constant region linked by the hinge region of human IgG₁ heavy chain constant region (see, FIG. 2).

In certain embodiments, the fusion protein of the present invention comprises cat allergen Fel d1 protein (or a portion thereof) and the CH2 and CH3 portion of human IgG₁ heavy chain constant region linked by the hinge region of human IgG₁ heavy chain constant region (see, FIG. 3).

In certain embodiments, the fusion protein of the present invention comprises peanut allergen Ara protein (or a portion thereof) and the CH2 and CH3 portion of human IgG₁ heavy chain constant region linked by the hinge region of human IgG₁ heavy chain constant region (see, FIG. 4).

The fusion proteins of the present invention are capable of specific binding of a native IgE molecule via its first polypeptide and specific binding of a native IgG inhibitory receptor comprising an ITIM via its second polypeptide. Such specific binding may be tested using any known assays, such as competitive binding assays including RIAs and ELISAs. Protein-protein complexes (e.g., complexes formed between the fusion protein and a native IgE molecule, between the fusion protein and a native IgG inhibitory receptor comprising an ITIM, and among the fusion protein, a native IgE molecule, and a native IgG inhibitory receptor comprising an ITIM) can be identified and isolated using various methods such as filtration, centrifugation, and flow cytometry. The assays may be performed using a purified protein of interest (e.g., a first or second polypeptide sequence of a fusion protein of the present invention, a fusion protein of the present invention, a native IgE molecule, or a native IgG inhibitory receptor comprising an ITIM), intact cells expressing a protein of interest, or cell lysate containing a protein of interest. The protein of interest may be immobilized or labeled prior to or during the assays.

The fusion proteins of the present invention may be prepared using standard techniques of recombinant DNA technology.

In a related aspect, the present invention provides a nucleic acid molecule comprising a nucleotide sequence encoding the fusion proteins described herein. In certain embodiments, the nucleic acid molecule comprises a nucleotide sequence encoding a fusion protein that comprises an allergen sequence capable of specifically binding to a native IgE molecule functionally linked to a second polypeptide sequence capable of specifically binding to a native IgG inhibitory receptor comprising an ITIM (e.g., FcεRIIb) via an IgG hinge region.

In certain embodiments, the nucleic acid molecule comprises a nucleotide sequence encoding a fusion protein that comprises a native allergen polypeptide sequence or a portion thereof linked to the CH2—CH3 portion of human IgG₁ heavy chain constant region via the hinge region of human IgG₁ heavy chain constant region.

In certain embodiments, the nucleic acid molecule comprises a nucleotide sequence encoding the katcin fusion protein that comprises a portion of cat allergen Fel d1 and the hinge-CH2—CH3 portion of human IgG1 as set forth in SEQ ID NO:17.

In certain embodiments, the nucleic acid molecule comprises a nucleotide sequence encoding the katcin fusion protein and has a nucleotide sequence as set forth in SEQ ID NO:16.

In certain embodiments, the nucleic acid molecule comprises a nucleotide sequence encoding a fusion protein of the present invention and is capable of specifically binding to SEQ ID NO:16 or its full length complement under stringent hybridization and wash conditions.

“Stringent hybridization and wash conditions” are defined as hybridization in 50% formamide, 6×SSC (0.75 M NaCl, 0.075 M sodium citrate), 50 mM sodium phosphate (pH 6.8), 0.1% sodium pyrophosphate, 5× Denhardt's solution, sonicated salmon sperm DNA (100 μg/ml), 0.5% SDS, and 10% dextran sulfate at 42° C. for at least 12 hours, with washes in 2×SSC (sodium chloride/sodium citrate) containing 0.1% SDS at 42° C. for 30 minutes twice and 0.2×SSC containing 0.1% SDS at 42° C. for 30 minutes.

The nucleic acid molecules encoding the fusion proteins of the present invention may be obtained via standard recombinant DNA techniques, chemical synthesis, or the combination thereof. For example, the coding sequences of various portions of the fusion proteins (e.g., first and second polypeptide sequences, and IgG hinge regions) may be obtained from natural sources or synthesized. Such sequences may be appropriately linked to produce the nucleic acid molecules encoding the fusion proteins of the present invention using various commercially available cloning and/expression vectors (e.g., those available from companies such as Invitrogen, San Diego, Calif.).

In certain embodiments, the present invention provides vectors comprising and capable of expressing the nucleotide sequences encoding the fusion proteins described herein. In certain embodiments, the vector comprises a nucleic acid sequence encoding the katcin fusion protein as set forth in SEQ ID NO:17. In certain embodiments, the vector comprises a nucleic acid sequence encoding the katcin fusion protein and has a nucleotide sequence as set forth in SEQ ID NO:16.

The vectors of the present invention include those useful for recombinant production in E. coli, S. cerevisiae strains of yeast, a baculovirus expression system for production in insect cells, fungal cells, avian cells, mammalian cells such as Chinese Hamster Ovary cells, and plant cells.

In one aspect, the present invention provides host cells transformed with the vectors described herein. Host cells useful for transformation with the vectors of the present invention include prokaryotic and eukaryotic host cells such as bacterial cells (e.g., E. coli cells), yeast cells (e.g., S. cerevisiae cells), insect cells, fungal cells, insect cells, mammalian cells, avian cells, and cells of higher plants.

Construction of expression systems suitable for desired hosts are known in the art. For recombinant production of the fusion protein of the present invention, the DNA encoding the fusion protein is suitably ligated into the expression vector of choice and then used to transform the compatible host. The transformed host cells are then cultured and maintained under conditions appropriate for expression of the foreign gene. The fusion protein of the present invention thus produced is recovered from the culture, either by lysing the cells or from the culture medium as appropriate and known in the art. Such fusion protein may be further purified if needed using standard techniques known in the art.

Alternatively, the fusion proteins of the present invention may be produced by chemical synthesis. Such methods are well known in the art and employ either solid or solution phase synthesis methods. Information about chemical synthesis of proteins may be found, for example, in Stewart and Young, Solid Phase Peptide Synthesis, 2nd Ed., Pierce Chemical Co., Rockford, Ill., 1984; Barany and Merrifield, The Peptide: Analysis Synthesis, Biology, editors E. Gross and J. Meienhofer, Vol. 2, Academic Press, New York, 1980; and Bodansky, Principles of Peptide Synthesis, Springer-Verlag, Berlin, 1984.

In one aspect, the present invention provides pharmaceutical compositions that comprise the fusion proteins of the present invention and pharmaceutically acceptable ingredients, such as physiologically acceptable excipients, additives, carriers or diluents. Suitable physiological acceptable ingredients are described in Remington's Pharmaceutical Sciences, 18^(th) Edition, Mack Publishing Co., Easton, Pa., 1990. Additional exemplary physiological acceptable ingredients include coloring, stabilizing agents, osmotic agents, and antibacterial agents.

The fusion proteins of the present invention may be used as vaccines, and thus also referred to as “allergen vaccine proteins.” Accordingly, in one aspect, the present invention provides methods for ameliorating or reducing the risk of an IgE-mediated allergic disease, comprising administering to a patient in need thereof an effective amount of the fusion proteins described herein. In certain embodiments, the present invention provides a method for ameliorating or reducing the risk of cat allergy, comprises administering to a patient in need thereof an effective amount of the katcin fusion protein with the amino acid sequence as set forth in SEQ ID NO:17.

A disease is “ameliorated” if the symptoms of the disease are alleviated, the extent of the disease is diminished, the progression of the disease is delayed or slowed, the disease state is ameliorated or palliated, and/or partial or total remission occurs.

The risk of a disease is “reduced” if the likelihood of a patient to have the disease is reduced, or the onset of the disease in a patient is delayed.

A “patient in need” refers to a patient already with an allergic disease or is prone to have an allergic disease. The patient may be a human or a non-human mammalian subject.

An “effective amount” is an amount sufficient to effect beneficial or desired therapeutic (including preventive) results. An effective amount can be administered in one or more administrations.

The IgE-mediated allergic diseases that the fusion proteins of the present invention are useful in ameliorating or reducing the risk of the diseases include, but are not limited to, allergic asthma, allergic rhinitis, hay fever, food allergy, such as those caused by peanut or other nuts, shellfish, milk, fish, soy, wheat, and egg, atopic dermatitis, pet allergy (e.g., cat allergy and dog allergy), eczema, drug allergy, chronic urticaria, ear infections associated with allergy, angioedema, allergy caused by pollen, mold, dust mite droppings, insect stings, or cockroaches or other insects, and anaphylactic shock.

The fusion proteins or pharmaceutical compositions of the present invention may be administered by any means that enables the fusion proteins to reach the targeted cells. These methods include, but are not limited to, oral, topical, transdermal, subcutaneous, intravenous, intramuscular, intra-arterial, intranasal, intrapulmonary, and intraparenteral modes of administration. The fusion proteins may be administered singularly or in combination with other compounds useful for anti-IgE therapy or allergen immunotherapy.

In certain embodiments, the fusion proteins or pharmaceutical compositions of the present invention are administered by inhalation. In certain other embodiments, the fusion proteins or pharmaceutical compositions of the present invention are administered by injection.

For parenteral administration, the fusion proteins of the invention can be, for example, formulated as a solution, suspension, emulsion or lyophilized powder in association with a physiologically acceptable parenteral vehicle such as water, saline, Ringer's solution, dextrose solution, and 5% human serum albumin. Liposomes and nonaqueous vehicles such as fixed oils may also be used. For example, a parenteral composition suitable for administration by injection is prepared by dissolving 1.5% by weight of active ingredient in 0.9% sodium chloride solution. The compositions of the present invention may be administered as a single dose or in multiple doses.

The compositions of the present invention may be provided in the form of an oral liquid, tablet, or capsule, nasal spray, aerosol, suspension, solution, emulsion, and/or eye drop. The appropriate dosage can be extrapolated from the dosages that indicate efficacy in vitro or in animal studies. The dosage administered varies depending upon factors such as: pharmacodynamic characteristics; its mode and route of administration; age, health, and weight of the recipient; nature and extent of symptoms; type of concurrent treatment; and frequency of treatment. Usually, the dosage of the fusion protein can be about 0.01 to 100 mg/kg of body weight, such as about 0.1 to 100, 0.05 to 50, or 1.0 to 10 mg/kg of body weight. The fusion proteins or pharmaceutical compositions may be administered to an individual per day in divided doses one or more times per day to obtain desired results.

The following example is provided for illustration of, not for limitation to, the present invention.

EXAMPLE

Construction of Katcin Fusion Protein

The human genomic IgG₁ DNA was obtained by using polymerase chain reaction. More specifically, human B cells were purified from peripheral blood and the genomic IgG₁ DNA was isolated and used as the template for a polymerase chain reaction. The 5′-end primer for IgG₁ Fc region is 5′-GG GGATCC GAG CCC AAA TCT TGT GAC-3′ (SEQ ID NO:11), containing a BamH I site, and 3′-end primer is 5′-GT GCGGCCGC TCA TTT ACC CGG AGA CAG GGA GAG-3′ (SEQ ID NO:12), containing a Not I site. After amplification, the PCR product was cloned into pCR4-TOPO vector (Invitrogen) and the sequences were confirmed. Nucleotide sequence analysis of the clones revealed that they contained full-length IgG₁ Fc genomic DNA from the hinge to CH3. These sequences matched the genomic DNA sequence of the corresponding region of human IgG₁ in the GenBank database (SEQ ID NO:15). The human IgG₁ Fc genomic DNA fragment was then subcloned into pSecTag2 (Invitrogen) vector.

The cat allergen Fel d1 cDNA was obtained by reverse transcription PCR. mRNA was prepared from cat epithelial cells and after reverse transcription, the resulting cDNA was used as template for PCR. The 5′-end primer for the PCR reaction is 5′-GGCCCAGCCGGCC GAA ATT TGC CCA GCC GTG-3′ (SEQ ID NO:13), containing a Sfi I site, and 3′-end primer for the PCAT reaction is 5′-GGATCC TCT CCC CAA AGT GTT CAG-3′ (SEQ ID NO:14), containing a BamH I site. The PCR products were cloned into pCR4-TOPO vector (Invitrogen) and the sequences were confirmed.

The Fel d1 cDNA was subcloned into pSecTag2 vector (Invitrogen) and fused with the human IgG₁ Fc genomic DNA fragment. The resulting construct encodes the protein katcin. The nucleotide sequence encoding katcin and the amino acid sequence of katcin are set forth in SEQ ID NOS:16 and 17, respectfully. The katcin protein comprises from its N-terminus to its C-terminus: a leader sequence, a portion of Fel d1 chain 1 (as set forth in SEQ ID NO:18), a linker sequence, a portion of Fel d1 chain 2 (as set forth in SEQ ID NO:19), IgG₁ hinge (as set forth in SEQ ID NO:20), and IgG₁ CH2-CH3 (as set forth in SEQ ID NO:21).

The expression vector containing the nucleic acid sequence encoding katcin was transfected into CHO-k1 cells (ATCC). After selection with 500 ug/ml of Zeocin (Invitrogen), a stable expression cell line expressing the katcin fusion protein was obtained. The katcin fusion protein was purified from the cell culture supernatants by using protein A affinity chromatography (Amersham Pharmacia).

Western Blot Analysis of Katcin Fusion Protein

Katcin fusion proteins were purified from several clones (HC1, HC2, HC3, HC4, HC10, and HC20) and mixed with standard SDS-PAGE loading buffer (Invitrogen) that containing protease inhibitors (1 μg/ml leupeptin, 1 μg/ml aprotinin, and 2 mM phenylmethylsulfonyl fluoride). Protein concentrations were determined using a Bio-Rad protein assay. 10 μg fusion proteins purified from various clones were subjected to SDS-PAGE under reducing condition, and then transferred to nitrocellulose membranes. The membranes were incubated with primary antibody (anti-Fel d1 monoclonal antibody) after blocking with 10% non-fat milk followed by incubation with horseradish peroxidase-conjugated anti-mouse secondary antibody. Visualization was performed using the chemiluminescence detection solution and analysis by X cell sure Lock tm Electrophoresis cell.

The results (FIG. 5) show that katcin proteins purified from various clones were of the expected molecular weight and were specific to the anti-Fel d1 antibody.

ELISA Assay for Katcin Binding Specificity for Fel D1 and IgG Fcr

100 μl of 1:500 dilution of anti-Fel d1 antibody (200 μg/ml) (100 μL/well) was incubated per well in flat-bottomed 96-well microliter plates overnight at 4° C. Plates were washed three times with phosphate-buffered saline (PBS), and blocked with PBS containing 0.01% Tween-20 (PBST) at room temperature (RT) for 2 h. Plates were then incubated with 100 μL/well of katcin protein at 4° C. overnight, washed three times with PBST, incubated with 100 μL alkaline phosphatase-conjugated goat anti human IgG Fc antibody for 2 hours at room temperature and then washed four times with PBST. Bound proteins were detected using BluePhos Microwell Phosphatase substrate (KPL, manufacturer's directions) and analyzed using a μQuant (Biotek, Winooski, Vt.) plate reader at 450 nm. Values represent the mean of triplicate experiments.

The results (FIG. 6) show that katcin proteins were correctly expressed in various clones and cound be recognized by anti-Fel D1 and anti-human IgG antibodies.

Inhibition of Passive Cutaneous Anaphylaxis (PCA) by Katcin in Monkey

A monkey was intradermally sensitized on the leg skin by cat allergy patient serum (Plasma International Inc) plus different doses of katcin fusion protein or control human myeloma IgE. Four hours later, the animal was intravenously given 10 μg of purified Fel d1, plus 5 ml of 0.5% Evans Blue dye. Sites were photographed 30 minutes later and largest diameter of bluing measured.

The results (FIG. 7) show that katcin specifically inhibited cat serum-induced IgE-medicated allergic reaction in vivo.

All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

1. A fusion protein comprising (i) a first polypeptide sequence capable of specifically binding to a native IgE molecule, (ii) a second polypeptide sequence capable of specifically binding to a native IgG inhibitory receptor comprising an immune receptor tyrosine based inhibitory motif (ITIM), and (iii) an IgG hinge region, wherein the first polypeptide sequence comprises an allergen sequence, the first polypeptide sequence and the second polypeptide sequence is functionally connected via the IgG hinge region, and the fusion protein comprises the amino acid sequence as set forth in SEQ ID NO:17.
 2. A pharmaceutical composition comprising the fusion protein of claim 1 and a pharmaceutically acceptable ingredient. 